Difficulty: Foundational. Prerequisites: none, this is typically the starting module.
Managerial accounting starts with understanding how costs behave: some costs trace directly to a product, others do not; some move with volume, others stay fixed. Cost-volume-profit (CVP) analysis uses this distinction to calculate breakeven points and guide short-run pricing and product-mix decisions. When a business faces a binding constraint (limited machine time, limited labour hours), the right metric is contribution margin per unit of the scarce resource, not contribution margin per unit sold.
Direct costs
Costs that can be physically traced to a specific cost object in an economically feasible way. In simple terms, you can point at the product and say "that material went into that unit."
Indirect costs (overhead / OH)
Costs that cannot be traced to a cost object in an economically feasible way and must be allocated instead. Think of it as the shared expenses that benefit many products but belong to none individually.
Variable costs
Costs that change in total in proportion to changes in output volume. In simple terms, make more units, spend more; make fewer, spend less.
Fixed costs
Costs that remain the same in total regardless of how many units are produced within the relevant range. Think of it as the bills you pay whether or not you produce anything.
Committed costs
Fixed costs locked in by prior decisions and not reducible in the short term. Examples: building depreciation, long-term lease payments.
Discretionary costs
Fixed costs that management can increase or cut in the short term. Examples: advertising spend, R&D budgets.
Cost object
Anything for which costs are measured, such as a product, a service line, a customer, or a department.
Cost hierarchy (activity levels)
A classification of costs by the level at which they are incurred:
Unit-level: incurred for every single unit produced (direct materials, direct labour, variable overhead)
Batch-level: incurred once per batch or production run (machine setups, material handling)
Product-level: incurred to support an entire product line (product design, product-line marketing)
Customer-level: incurred for specific customers (custom logos, customer-specific licensing)
Facility-level: incurred to keep the facility running regardless of products or customers (plant depreciation, insurance, production manager salary)
Manufacturing costs
All costs of producing goods: direct materials + direct labour + manufacturing overhead.
Non-manufacturing costs (period costs)
Selling and administrative costs. These are expensed in the period incurred and never attach to inventory.
Contribution margin (CM)
Revenue minus all variable costs (both manufacturing and non-manufacturing). In simple terms, the amount each unit contributes toward covering fixed costs and generating profit.
Breakeven point
The volume of sales at which total contribution margin exactly equals total fixed costs, so net income is zero.
Relevant cost
A cost that differs between decision alternatives and therefore matters for a particular decision. Includes opportunity costs.
Opportunity cost
The profit forgone by choosing one alternative over the next best option. In simple terms, it is what you give up.
Sunk cost (irrelevant cost)
A cost already incurred in the past that no future decision can change. In simple terms, money already spent, so ignore it when deciding what to do next.
Constraint (bottleneck)
The scarce resource that limits a firm's output, such as machine hours, labour hours, or raw-material supply. Decisions should maximise contribution margin per unit of the constrained resource.
Every cost can be classified along two independent dimensions. The first is traceability: direct costs trace to a cost object, indirect costs do not and must be allocated through a cost pool. The second is behaviour: variable costs move with output volume, fixed costs do not.
These two dimensions are independent. A cost can be direct and variable (tyres used on a specific car model), direct and fixed (salary of a supervisor dedicated to one assembly line), indirect and variable (metered electricity in a shared plant), or indirect and fixed (annual lease on a shared facility).
Costs also fall into a hierarchy based on what triggers them:
Unit-level costs rise with each additional unit: direct materials, direct labour, utilities to run production equipment
Batch-level costs arise once per production run: machine setup, material handling to deliver raw materials to the line
Product-level costs support an entire product line regardless of units or batches: product design, product-specific marketing
Customer-level costs serve specific customers: custom packaging, customer-specific logo licensing
Facility-level costs sustain the organisation's infrastructure: plant depreciation, insurance, production manager salary
The hierarchy matters because traditional costing systems allocate overhead using a single volume-based driver (such as direct labour hours), which assumes all overhead is unit-level. When overhead includes significant batch-level, product-level, or facility-level components, a single driver distorts product costs.
The variable costing income statement separates all costs by behaviour rather than by function:
Revenue (Price x Quantity)
Less: all variable costs (manufacturing and non-manufacturing)
Equals: contribution margin
Less: all fixed costs (manufacturing and non-manufacturing)
Equals: net income
This format is preferred for short-run decision-making because everything above the contribution margin line varies with volume and everything below it does not. In the short run, only variable costs are decision-relevant (in general). In the long run, all costs are on the table.
Unit contribution margin = selling price per unit minus variable cost per unit.
Breakeven volume = total fixed costs / unit contribution margin.
At the breakeven volume, contribution margin exactly covers fixed costs and net income is zero. Each unit sold beyond breakeven contributes its full unit CM to profit.
Giberson is a skilled glassblower whose business is unprofitable despite strong sales. The case illustrates decision-making when a single resource constrains output.
The constraint is Giberson's time, particularly his "hot time" (actual glass-blowing). Virtually all other costs are fixed and do not change with the product mix.
He works roughly 40 weeks per year (52 minus 12 weeks of travel). His claimed 30 hours per week of productive work turns out to be only about 18.6 hours of hot time and 24.3 hours total (hot plus cold finishing time).
Because all costs are fixed, cost allocation is irrelevant. The pricing question reduces to: how much must each minute of constrained time earn?
Pricing by the minute: total annual costs ($50,352) / total productive minutes (30 hours x 40 weeks x 60 = 72,000 minutes) = $0.70 per minute. Each product is priced by multiplying its production time by this rate.
If prices are given by the market, the optimal product mix maximises contribution margin per minute of the constrained resource, not contribution margin per unit.
Contribution margin per minute for each product: patterned glasses $9/18 min = $0.50/min; paperweights $15/30 min = $0.50/min; wrapped tumblers $8/18 min = $0.44/min; vases $25/30 min = $0.83/min.
Giberson should produce vases until demand is satisfied, then fill remaining time with patterned glasses or paperweights.
He should dedicate all his time to hot work (his value-added activity) and hire a part-time worker for cold finishing.
When all costs are fixed, cost allocation adds no information for decision-making.
The binding constraint determines the relevant metric: CM per unit of the scarce resource.
If the producer sets prices, charge per minute of constrained time. If the market sets prices, rank products by CM per minute and produce in that order.
\text{Unit CM} = P - \text{Unit VC}\text{Net Income} = (\text{Unit CM} \times q) - FC\text{Breakeven Volume} = \frac{FC}{\text{Unit CM}}\text{Breakeven Volume} = \frac{\text{Fixed Cost}}{\text{Selling Price per Unit} - \text{Variable Cost per Unit}}\text{CM per minute of constraint} = \frac{\text{Contribution Margin per Unit}}{\text{Minutes of Constrained Resource per Unit}}Where P = unit selling price, q = quantity sold, VC = variable cost per unit, FC = total fixed costs.
CVP example (Mountain Bike): price $120, fixed OH $480,000, DM $30/unit, DL $15/unit, variable OH $15/unit. Unit VC = $60. Unit CM = $60. Breakeven = $480,000 / $60 = 8,000 units.
CVP analysis is how any business with significant fixed costs decides its minimum viable scale. A restaurant calculates how many covers per night it needs to break even. A SaaS company works out how many subscribers justify its server and engineering costs. The Giberson case shows the same logic in a craft business: when one person's time is the bottleneck, every product should be priced and prioritised based on what it earns per minute of that person's time. This is the same principle behind why consulting firms bill by the hour and why factories prioritise products with the highest CM per machine-hour.
Students often think "indirect" means the same as "fixed." It does not. A cost can be indirect and variable (shared electricity metered to a multi-product plant) or direct and fixed (a dedicated supervisor's salary).
Students often confuse sunk costs with fixed costs. Fixed costs recur each period and are relevant for long-run decisions. Sunk costs are past expenditures that no decision can undo.
Students sometimes compute breakeven by dividing fixed costs by the selling price rather than by the unit contribution margin. The denominator must be CM per unit, not price.
Students often pick the product with the highest contribution margin per unit as the most profitable. When a constraint exists, the right ranking is CM per unit of the scarce resource.
Be ready to classify any cost along both dimensions (direct/indirect AND variable/fixed) simultaneously. Exam questions frequently present a cost and ask for its classification on a 2x2 grid.
Know the CVP income statement format cold: revenue, minus variable costs, equals CM, minus fixed costs, equals net income.
Breakeven volume = FC / Unit CM. Expect a numerical problem.
When a constraint is introduced, switch your decision metric from CM per unit to CM per unit of the constrained resource. This is a very common exam twist.
Giberson's case is a frequent reference: all costs fixed, time is the constraint, cost allocation is unnecessary, price by the minute or rank by CM per minute.
True or false: all indirect costs are fixed costs. (False)
Fill in the blank: breakeven volume equals total fixed costs divided by ______. (unit contribution margin)
True or false: sunk costs should be included when evaluating a new decision. (False)
Fill in the blank: when a resource constraint exists, products should be ranked by contribution margin per ______. (unit of the constrained resource)
True or false: in CVP analysis, the variable costing format separates costs by function (manufacturing vs selling). (False, it separates by behaviour: variable vs fixed)
Q: A company sells a product for $80 per unit. Variable costs are $50 per unit and total fixed costs are $150,000. What is the breakeven volume in units?
A: Unit CM = $80 - $50 = $30. Breakeven volume = $150,000 / $30 = 5,000 units.
Q: Giberson's Glass Studio has total annual costs of $50,352 and 72,000 productive minutes per year. What price should he charge for an item that takes 18 minutes of hot time?
A: Cost per minute = $50,352 / 72,000 = $0.70. Price for an 18-minute item = 18 x $0.70 = $12.60.
Q: A factory makes two products on the same machine. Product A has a CM of $20 per unit and takes 4 machine-hours. Product B has a CM of $12 per unit and takes 2 machine-hours. Machine capacity is limited. Which product should be prioritised?
A: CM per machine-hour: A = $20/4 = $5/hr; B = $12/2 = $6/hr. Prioritise Product B because it earns more per unit of the constrained resource.
Q: A business owner paid $12,000 for a car five years ago, spent $2,000 on repairs two years ago, and now faces a $5,000 repair bill. Which of these costs are relevant to the decision of whether to repair the car?
A: Only the $5,000 future repair cost is relevant. The $12,000 purchase price and $2,000 past repair are sunk costs.
Q: Why is cost allocation unnecessary in Giberson's case?
A: Because all of Giberson's costs are fixed. Regardless of what he produces, his total costs do not change. Cost allocation adds no information for pricing or product-mix decisions when there are no variable costs to trace.
This material connects directly to cost allocation systems (traditional costing, ABC, TDABC), which extend the idea that different costs behave differently and should be assigned using drivers that reflect actual resource consumption. It also feeds into variance analysis, where actual costs are compared against standard (expected) costs at the actual volume, using the flexible budget concept that rests on the variable/fixed distinction covered here.
Related Terms / Search Tags
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